A conventional circuit breaker comprises a fuse arranged between a switch and a circuit such that when an electrical overloading occurs, the fuse melts before the overloading causes damages to the circuit. However, if the fuse is not properly installed or an improper fuse is used, the overloading current cannot melt the fuse, leading to a disaster. U.S. Pat. Nos. 5,262,748, 4,167,720, 4,937,548, 5,223,813, 5,451,729, and 5,558,211 disclose different types of circuit breakers that all include a complicated mechanism to drive a bimetallic plate which is expected to deform and bend when an overloading occurs. Nevertheless, it is noted that the bimetallic plate does not always deform as desired to trigger the protection mechanism because the plate may not be allowed to freely deform, and remains in contact with the terminal so that sparks are produced and therefore cause disaster.
Therefore, it is desired to have a protection mechanism for a switch device that provides a space sufficient to allow the bimetallic plate to properly deform when an overloading occurs in order to resolve the shortcomings of the conventional switch devices.